This invention relates to a method for the plasma removal of photoresist. More specifically, this invention relates to a method for the removal of photoresist from an oxidizable substrate through the use of hydrogen plasma.
Patterned photoresist layers are often used as etch masks for etching a pattern in an underlying substrate. A photosensitive material is applied to the surface of a substrate and photolithographically patterned. The substrate coated with photoresist is then subjected to an etchant which etches those portions of the substrate which are exposed through the photoresist layer. The pattern in the photoresist layer is thus replicated in the substrate surface. After serving as an etch mask, the photoresist layer must be removed from the surface of the substrate. The photoresist layer, which is typically a polymerized organic film, can be removed by dissolution in an organic solvent. The photoresist layer can also be removed by a dry process known as "ashing". Ashing is a technique or process by which the photoresist layer is exposed to an oxygen plasma. The highly reactive oxygen plasma reacts with or oxidizes the organic photoresist layer. The oxidation or combustion products resulting from the ashing operation are volatile and are carried away in a gas stream. Ashing is preferred to wet chemical removal because fewer process steps are involved, less handling of the substrates is required, chemicals and chemical handling equipment are reduced, and ashing is more environmentally acceptable.
A major problem with the ashing process is that the highly reactive oxygen plasma can react in a deleterious manner with an oxidizable substrate material. Even using very dilute oxygen mixtures has not overcome this problem and does, at the same time, significantly slow the reaction. Ashing is thus limited to the removing of photoresist from nonoxidizable or only slowly oxidizable substrates.
Accordingly, it is an object of this invention to provide an improved dry photoresist stripping technique.
It is a further object of this invention to provide an environmentally acceptable photoresist removal process which does not adversely effect the underlying substrate.